Organo-soluble phosphinated polyimides from asymmetric diamines

Two new asymmetric diamines (1-2) were prepared via a facile, one-pot procedure. Based on diamine (1-2), a series of asymmetric polyimides (3-4) were prepared in NMP/xylene by high-temperature solution polymerization. The resulting polyimides are readily soluble in some organic solvents, and can be solution casted into flexible and creasable films. An intramolecular charge complex mechanism was proposed to the structure-optical transparency relationship. Polyimides 3-4 display high-Tg (319-401 °C), high moduli (2.40-7.20 GPa), moderate coefficient of thermal expansion (38-53 ppm/°C), and excellent flame retardancy. These results show that the introduction of the asymmetric structure is an effective way to improve organo-solubility while maintaining thermal properties. Because of these properties, polyimides 3-4 can be considered as excellent high-Tg and flame-retardant materials for microelectronic applications.     

Analysis of compressive strength and subsidence of a vertebral body cage with Taguchi methods

Abstract

A titanium mesh cage (TMC) might develop subsidence and cause local kyphotic deformity of the spine. For prevention of this complication, this study was designed to find the most appropriate spike design for a vertebral body cage (VBC). In order to investigate the subsidence of a VBC, three‐dimensional finite element models of the L₅ spinal model with a nonlinear contact analysis have been developed. Then, the Taguchi robust design method was used to evaluate spike designs. Finally, the mechanical experiment was developed to obtain the compressive strength of the VBC. For the results of the FEM‐based Taguchi method, the spike row, the spike obliquity, and the spike height were especially important factors for preventing the subsidence. The optimum combinations were pyramidal spike type, a spike height of 2 mm, a spike diameter of 1.4 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 10 mm. For the results of the experiment, the good relationship between finite element simulation and mechanical testing was found with a correlation coefficient of 0.847. The FEM‐based Taguchi method could decrease the effort and time for analyzing the spike factors of the VBC and the mechanical tests might provide the useful evidence to prove the applicability of the finite element models.     

Evolution of solids fraction surfaces in tapping: simulation and dynamical systems analysis

We report our findings on the evolution of solids fraction in a tapped system of inelastic, frictional spheres as a function of the applied acceleration obtained via discrete element simulations. Animations of the simulation data reveal the propagation of a wave initiated from the base that causes local rearrangements of the particles ultimately leading to the development of a dense microstructure. We also describe the analysis of dynamical models capable of predicting the simulated behavior, and advanced visualization techniques for revealing the dynamics.     

Inelastic post buckling behavior of very short column

Abstract

This paper presents an unconditionally stable implicit algorithm for the direct integration of a linear structural dynamic equation of motion. The algorithm is based on two simultaneous difference equations and a weighting factor G for solving displacement at the next time step. Unconditional stability is proven for the weighting factor G in the range from –0.466 to 0.140 in all undamped and damped cases. The unconditionally stable range of G can be extended, from –1.0 to 0.333, for certain types of structure. The amplitude decay and period variation are used as the basic parameters to compare the accuracy of the present algorithm with various other integration methods. A spring‐mass‐dashpot model is applied to illustrate the algorithm for transient and quasi‐static analyses.     

Linear defuzzified output of fuzzy controllers via mixed fuzzy logic operators

Abstract

The linear defuzzified output of a fuzzy controller with two fuzzy variable inputs and one output is discussed in this paper. Arbitrary amounts of triangular fuzzy numbers are employed to fuzzify the linguistic variables in fuzzy control rules. We show that the defuzzified output is exactly equivalent to a linear function of the inputs to the fuzzy controller by using three mixed fuzzy logic operators to evaluate the control rules.     

A novel normal walk model for PCS networks with mesh cell configuration

Abstract

Model‐based movement patterns play a crucial role in evaluating the performance of mobility‐dependent Personal Communication Service (PCS) strategies, such as location updating and paging schemes. In this study, we propose a novel normal walk model to represent the daily mobility patterns of a mobile station (MS) in mesh PCS networks more closely than does a conventional random walk model. The proposed model applies a drift angle, θ, to determine the next relative direction in which an MS will leave a mesh cell in one step, based on the concepts that most real trips follow the shortest path and the directions of daily motion are mostly symmetric. Thus, the probability of θ is assumed to approach a normal distribution with the parameters: μ is set to 0° and σ falls in the interval [5°, 90°]. Varying σcan redistribute the probabilities of θ to make the movement patterns more realistic to represent the mobility of users in PCS networks.

An analytical normal walk model is further formulated in a 6‐layer cluster with mesh cells for quantitative analysis. Experimental results demonstrate that for σ = 10°, 30°, 60°, and 90°, the discrepancies between the analytical computations (expected steps) and the simulated values (average steps) are all within ±0.55%, and most are within ±0.35%. Moreover, when σ is set to 79.5°, a normal walk can almost represent and even replace a random walk.     

The behavior of reinforcing bars under compression

Abstract

This paper presents a research on the stress‐strain relationship of reinforcing bars under compression tests. From the test observations, a yielding section is found to develop from a certain point and then to propagate throughout the entire longitudinal length. This behavior results in a transition stage of the longitudinal stress‐strain curve between the elastic and full plastic states. At this transition state, the lateral strain is closely related to the location of the clamped extensometer.     

Resolution enhancement of nondestructive testing from B‐scans

This article presents an approach to extend our previous work of the minimum‐weighted norm method in computerized tomography. In particular concentrating on applications of ultrasonic nondestructive testing, the resolution enhancement in the image reconstruction from B‐scans is achieved. To combat the degradation problem due to physical focus of finite‐sized ultrasonic transducer and incompleteness of B‐scan data, a profile‐oriented prior knowledge about the object being detected is incorporated in the image reconstruction, in the form of weighted summation of specific basis functions. Each basis function is characterized by an image of coherent illumination pattern associated with a specific measuring time and a specific measuring position. From the demonstrations with both simulated and experimental data values, this technique proves a great potential in improving the image quality. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 185–193, 2012     

A mood‐ and situation‐based model for developing intuitive Pop music recommendation systems

Traditionally, a per‐song‐purchased base recommendation system is used on most music websites, but this method produces unsatisfactory results under various situational practices. This study proposes a hybrid procedure that includes both an expert‐attributes selection capability and a mood/situation‐attributes categorization functionality. This procedure fosters the development of a so‐called MoMusic model as an unlimited online streaming service to replace current systems and artfully provide music to interested parties. This study employs a dataset consisting of 821 songs from the 2005–2010 annual music rankings as well as songs from the top artists from 2009 to 2010 from Taiwan's popular KKBOX music streaming service. The experimental dataset was assessed and coded by domain experts, and the expert‐attributes selections and mood/situation‐attributes categorizations were used to produce recommendation lists. These recommendation lists were then paired with questionnaire‐derived music preferences from experienced users. The experimental results conclusively show that the MoMusic model is approximately twice as accurate as the random selection‐based lists and the KKBOX‐like recommendation lists and performs better than the two listed recommendation systems. The MoMusic model scores 0.889 on the usefulness evaluation, whereas the system satisfaction is 0.96. The MoMusic model has the advantages of intuitive use and high performance.